This invention relates to an apparatus for reproduction of audio-visual material, particularly but not exclusively advertising material, in an environment subject to ambient noise.
It is known to provide, in an acoustic environment such as a large shop or shopping centre, apparatus for reproducing audio-visual advertising material. Such apparatus comprises one or more units each comprising a video tape player coupled to a monitor device displaying the taped material and reproducing the accompanying soundtrack. Generally, people within the environment will not always be watching the display on the monitor. However, their attention may be drawn to the monitor by the accompanying reproduced audio soundtrack.
A number of problems arise in the use of such a system. Firstly, the ambient noise within the environment may rise or fall in volume. A rise in volume may drown out the reproduced audio, so that attention is no longer drawn to the visual display and the apparatus ceases to be effective. On the other hand, a drop in the ambient volume can cause the reproduced audio to become obtrusive and to annoy people within the environment, and cause them to tend to avoid the apparatus and, possibly, the environment (e.g shop) in which it is positioned. Further, staff working within the environment, who will have to listen to the audio-visual material many times, will be fatigued by overloud reproduced audio, leading to reduced working efficiency and job satisfaction.
In the field of audio reproduction in general, several prior art automatic volume control devices are known; for instance, from GB485005, GB2214013, GB2211685, GB2207313, GB2074408, GB2029141 and U.S. Pat. No. 4254303, EP0027519, EP0026929 and WO88/01453. However, none of these relate to audio-visual reproduction apparatus comprising a plurality of distributed audio-visual reproduction stations.
According to the invention there is provided, in one aspect, audio visual reproduction apparatus comprising a common audio source and video source, and a plurality of display terminals each including volume control apparatus for keeping the generated audio level audible with respect to ambient noise in the environment of the device.
In another aspect, the invention provides volume control apparatus, which is arranged to control the gain of an audio amplifier by forming a difference between a signal derived from the amplifier output and a received audio signal from a microphone, the dependence of the difference upon the signal derived from the amplifier output exceeding that on the signal from the microphone so that the device exhibits a degree of compression related to the ambient noise. This is found to increase the acceptability of the volume control to listeners.
In another aspect, the invention provides a visual display system arranged to supply a plurality of output display devices from a common visual source arranged to switch between a plurality of different visual signals; in one preferred embodiment, a plurality of visual signals are stored on a medium and can be replayed in one or more desired sequences therefrom. In this embodiment, preferably, to allow access time between different stored locations on the medium, a second visual signal source (for example, a still picture held in a frame store) is provided between successive stored signals of the sequence.
Other aspects and preferred embodiments of the invention will be apparent from the following description and claims.